In recent years, what has been sought in light-sensitive silver halide photographic materials is that they can perform rapid processing, can have high image quality and yet superior processing stability, and can be of low cost. Particularly sought after are light-sensitive silver halide photographic materials that can be processed rapidly.
Light-sensitive silver halide photographic materials are usually continuously processed by an automatic processing machine, installed in all photofinishing laboratories. However, as an improvement in service to users, it is desirable to finish processing and to return the products to users on the day the development orders were received, and, nowadays, it is further desired even to return products within a few hours after the receipt of an order, whereby there is an increasing necessity for rapid processing. Development of rapid processing has also been hastened because a shortened processing time may bring about an increase in production efficiency and a cost decrease may thereby be made possible.
To achieve rapid processing, approaches have been made from two directions, i.e., the light-sensitive material and the processing solution. In respect of color developing processing, it has been attempted to raise the temperature, the pH and the concentration of a color developing agent, and also it is known to add additives such as development accelerators. The above development accelerators may include 1-phenyl-4-pyrazolidone, as disclosed in British Patent No. 811,185, N-methyl-p-aminophenol, as disclosed in U.S. Pat. No. 2,417,514, and N,N,N',N'-tetramethyl-p-phenylenediamine, as disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as Japanese Patent O.P.I. Publication) No. 15554/1975. The method in which these are used, however, cannot achieve sufficient rapidness, and may be often accompanied by a deterioration of performance such as an increase in fog.
On the other hand, the shape, size and composition of silver halide grains of a silver halide emulsion used in the light-sensitive material are known to greatly affect the development speed and so forth. In particular, it is known that the halogen composition may greatly affect the same, and that a very remarkably high development speed can be shown when a silver chloride-rich silver halide is used.
However, the silver chloride-rich silver halide is poor in long-term storage stability, and seriously susceptible to fog, particularly when stored under conditions of high temperature and high humidity. It also has a much lower speed compared with silver bromide-rich silver chlorobromide, silver bromide or silver iodobromide. To increase the speed of the silver chloride-rich silver halide, gold sensitization is most suitable (as well as sulfur sensitization), which, however, brings about an increase in fog as a property inherent in gold compounds, and also soft gradation at the toe of the characteristic curve. Increasing the amount of gold compounds may bring about suppression of the fog, but on the other hand may result in greater soft gradation, additionally accompanied by desensitization.
Another possibility known as a means for improving the fog in storage stability of raw stocks, is to use cyanuric acid (Japanese Patent O.P.I. Publication No. 201335/1985), but this is disadvantageous in that although the fog can be suppressed the desensitization becomes greater.
Therefore, the development of a light-sensitive silver halide photographic material having high speed, high gradient and low fog, and also being superior in stability and yet suited for rapid processing, is energetically sought.